Under 14 CFR § 107.52, may a remote pilot operate a small unmanned aircraft system with its transponder turned on?
Why: 14 CFR § 107.52 states that unless otherwise authorized by the Administrator, no person may operate a small unmanned aircraft system under part 107 with a transponder on.
This reverses the rule: transponder-on is prohibited by default under § 107.52, not required for traffic awareness.
Altitude is irrelevant to this prohibition; § 107.52 applies regardless of altitude, not only above 400 feet AGL.